llext: Add parameters to arch_elf_relocate

The RISC-V port of llext requires additional parameters for
handling non-adjacent HI20/LO12 relocations in arch_elf_relocate():
the current extension (struct llext), the current extension loader
(struct llext_loader), the current section header (elf_shdr_t) and
the current symbol (elf_sym_t).
This changes the signature of arch_elf_relocate accordingly.

Signed-off-by: Eric Ackermann <eric.ackermann@cispa.de>

arch/arc/core/elf.c

@@ -6,6 +6,7 @@
 
 #include <zephyr/llext/elf.h>
 #include <zephyr/llext/llext.h>
+#include <zephyr/llext/llext_internal.h>
 #include <zephyr/llext/loader.h>
 #include <zephyr/logging/log.h>
 #include <zephyr/sys/util.h>
@@ -31,12 +32,32 @@ LOG_MODULE_REGISTER(elf, CONFIG_LLEXT_LOG_LEVEL);
  * https://github.com/foss-for-synopsys-dwc-arc-processors/arc-ABI-manual/blob/master/ARCv2_ABI.pdf
  * https://github.com/zephyrproject-rtos/binutils-gdb
  */
-int arch_elf_relocate(elf_rela_t *rel, uintptr_t loc, uintptr_t sym_base_addr, const char *sym_name,
-		      uintptr_t load_bias)
+int arch_elf_relocate(struct llext_loader *ldr, struct llext *ext, elf_rela_t *rel,
+		      const elf_shdr_t *shdr)
 {
 	int ret = 0;
-	uint32_t insn = UNALIGNED_GET((uint32_t *)loc);
 	uint32_t value;
+	const uintptr_t loc = llext_get_reloc_instruction_location(ldr, ext, shdr->sh_info, rel);
+	uint32_t insn = UNALIGNED_GET((uint32_t *)loc);
+	elf_sym_t sym;
+	uintptr_t sym_base_addr;
+	const char *sym_name;
+
+	ret = llext_read_symbol(ldr, ext, rel, &sym);
+
+	if (ret != 0) {
+		LOG_ERR("Could not read symbol from binary!");
+		return ret;
+	}
+
+	sym_name = llext_symbol_name(ldr, ext, &sym);
+
+	ret = llext_lookup_symbol(ldr, ext, &sym_base_addr, rel, &sym, sym_name, shdr);
+
+	if (ret != 0) {
+		LOG_ERR("Could not find symbol %s!", sym_name);
+		return ret;
+	}
 
 	sym_base_addr += rel->r_addend;
 

arch/arm/core/elf.c

@@ -7,6 +7,7 @@
 
 #include <zephyr/llext/elf.h>
 #include <zephyr/llext/llext.h>
+#include <zephyr/llext/llext_internal.h>
 #include <zephyr/logging/log.h>
 #include <zephyr/sys/util.h>
 
@@ -316,11 +317,32 @@ static void thm_movs_handler(elf_word reloc_type, uint32_t loc,
  * Do NOT mix them with not 'Thumb instructions' in the below switch/case: they are not
  * intended to work together.
  */
-int arch_elf_relocate(elf_rela_t *rel, uintptr_t loc, uintptr_t sym_base_addr,
-			const char *sym_name, uintptr_t load_bias)
+int arch_elf_relocate(struct llext_loader *ldr, struct llext *ext, elf_rela_t *rel,
+		      const elf_shdr_t *shdr)
 {
 	int ret = 0;
 	elf_word reloc_type = ELF32_R_TYPE(rel->r_info);
+	const uintptr_t load_bias = (uintptr_t)ext->mem[LLEXT_MEM_TEXT];
+	const uintptr_t loc = llext_get_reloc_instruction_location(ldr, ext, shdr->sh_info, rel);
+	elf_sym_t sym;
+	uintptr_t sym_base_addr;
+	const char *sym_name;
+
+	ret = llext_read_symbol(ldr, ext, rel, &sym);
+
+	if (ret != 0) {
+		LOG_ERR("Could not read symbol from binary!");
+		return ret;
+	}
+
+	sym_name = llext_symbol_name(ldr, ext, &sym);
+
+	ret = llext_lookup_symbol(ldr, ext, &sym_base_addr, rel, &sym, sym_name, shdr);
+
+	if (ret != 0) {
+		LOG_ERR("Could not find symbol %s!", sym_name);
+		return ret;
+	}
 
 	LOG_DBG("%d %lx %lx %s", reloc_type, loc, sym_base_addr, sym_name);
 

arch/arm64/core/elf.c

@@ -6,6 +6,7 @@
 
 #include <zephyr/llext/elf.h>
 #include <zephyr/llext/llext.h>
+#include <zephyr/llext/llext_internal.h>
 #include <zephyr/logging/log.h>
 #include <zephyr/sys/util.h>
 #include <zephyr/sys/byteorder.h>
@@ -430,12 +431,32 @@ static int imm_reloc_handler(elf_rela_t *rel, elf_word reloc_type, uintptr_t loc
  * @retval -ENOTSUP Unsupported relocation
  * @retval -ENOEXEC Invalid relocation
  */
-int arch_elf_relocate(elf_rela_t *rel, uintptr_t loc, uintptr_t sym_base_addr, const char *sym_name,
-		      uintptr_t load_bias)
+int arch_elf_relocate(struct llext_loader *ldr, struct llext *ext, elf_rela_t *rel,
+		      const elf_shdr_t *shdr)
 {
 	int ret = 0;
 	bool overflow_check = true;
 	elf_word reloc_type = ELF_R_TYPE(rel->r_info);
+	const uintptr_t loc = llext_get_reloc_instruction_location(ldr, ext, shdr->sh_info, rel);
+	elf_sym_t sym;
+	uintptr_t sym_base_addr;
+	const char *sym_name;
+
+	ret = llext_read_symbol(ldr, ext, rel, &sym);
+
+	if (ret != 0) {
+		LOG_ERR("Could not read symbol from binary!");
+		return ret;
+	}
+
+	sym_name = llext_symbol_name(ldr, ext, &sym);
+
+	ret = llext_lookup_symbol(ldr, ext, &sym_base_addr, rel, &sym, sym_name, shdr);
+
+	if (ret != 0) {
+		LOG_ERR("Could not find symbol %s!", sym_name);
+		return ret;
+	}
 
 	switch (reloc_type) {
 	case R_ARM_NONE:

arch/riscv/core/elf.c

@@ -8,6 +8,9 @@
  */
 #include <zephyr/llext/elf.h>
 #include <zephyr/llext/llext.h>
+#include <zephyr/llext/llext_internal.h>
+#include <zephyr/llext/loader.h>
+
 #include <zephyr/logging/log.h>
 #include <zephyr/sys/util.h>
 
@@ -68,11 +71,32 @@ static long long last_u_type_jump_target;
  * https://github.com/riscv-non-isa/riscv-elf-psabi-doc/blob/master/riscv-elf.adoc
  *
  */
-int arch_elf_relocate(elf_rela_t *rel, uintptr_t loc_unsigned, uintptr_t sym_base_addr_unsigned,
-		      const char *sym_name, uintptr_t load_bias)
+int arch_elf_relocate(struct llext_loader *ldr, struct llext *ext, elf_rela_t *rel,
+		      const elf_shdr_t *shdr)
 {
 	/* FIXME currently, RISC-V relocations all fit in ELF_32_R_TYPE */
 	elf_word reloc_type = ELF32_R_TYPE(rel->r_info);
+	const uintptr_t load_bias = (uintptr_t)ext->mem[LLEXT_MEM_TEXT];
+	const uintptr_t loc_unsigned = llext_get_reloc_instruction_location(ldr, ext,
+									    shdr->sh_info, rel);
+	elf_sym_t sym;
+	uintptr_t sym_base_addr_unsigned;
+	const char *sym_name;
+	int ret;
+
+	ret = llext_read_symbol(ldr, ext, rel, &sym);
+	if (ret != 0) {
+		LOG_ERR("Could not read symbol from binary!");
+		return ret;
+	}
+
+	sym_name = llext_symbol_name(ldr, ext, &sym);
+	ret = llext_lookup_symbol(ldr, ext, &sym_base_addr_unsigned, rel, &sym, sym_name, shdr);
+
+	if (ret != 0) {
+		LOG_ERR("Could not find symbol %s!", sym_name);
+		return ret;
+	}
 	/*
 	 * The RISC-V specification uses the following symbolic names for the relocations:
 	 *
@@ -99,7 +123,7 @@ int arch_elf_relocate(elf_rela_t *rel, uintptr_t loc_unsigned, uintptr_t sym_bas
 	long long original_imm8, jump_target;
 	int16_t compressed_imm8;
 	__typeof__(rel->r_addend) target_alignment = 1;
-	const intptr_t sym_base_addr = (intptr_t)sym_base_addr_unsigned;
+	intptr_t sym_base_addr = (intptr_t)sym_base_addr_unsigned;
 
 	LOG_DBG("Relocating symbol %s at %p with base address %p load address %p type %" PRIu64,
 		sym_name, (void *)loc, (void *)sym_base_addr, (void *)load_bias,

include/zephyr/llext/llext.h

@@ -354,18 +354,19 @@ int llext_add_domain(struct llext *ext, struct k_mem_domain *domain);
  * symbolic data such as a section, function, or object. These relocations
  * are architecture specific and each architecture supporting LLEXT must
  * implement this.
+ * Arguments sym_base_addr, sym_name can be computed from the sym parameter,
+ * but these parameters are provided redundantly to increase efficiency.
  *
+ * @param[in] ldr Extension loader
+ * @param[in] ext Extension being relocated refers to
  * @param[in] rel Relocation data provided by ELF
- * @param[in] loc Address of opcode to rewrite
- * @param[in] sym_base_addr Address of symbol referenced by relocation
- * @param[in] sym_name Name of symbol referenced by relocation
- * @param[in] load_bias `.text` load address
+ * @param[in] shdr Header of the ELF section currently being located
  * @retval 0 Success
  * @retval -ENOTSUP Unsupported relocation
  * @retval -ENOEXEC Invalid relocation
  */
-int arch_elf_relocate(elf_rela_t *rel, uintptr_t loc,
-			     uintptr_t sym_base_addr, const char *sym_name, uintptr_t load_bias);
+int arch_elf_relocate(struct llext_loader *ldr, struct llext *ext, elf_rela_t *rel,
+		      const elf_shdr_t *shdr);
 
 /**
  * @brief Locates an ELF section in the file.

include/zephyr/llext/llext_internal.h

@@ -11,6 +11,8 @@
 extern "C" {
 #endif
 
+#include <zephyr/llext/llext.h>
+
 /**
  * @file
  * @brief Private header for linkable loadable extensions
@@ -18,8 +20,6 @@ extern "C" {
 
 /** @cond ignore */
 
-struct llext_loader;
-struct llext;
 
 struct llext_elf_sect_map {
 	enum llext_mem mem_idx;
@@ -28,6 +28,39 @@ struct llext_elf_sect_map {
 
 const void *llext_loaded_sect_ptr(struct llext_loader *ldr, struct llext *ext, unsigned int sh_ndx);
 
+
+static inline const char *llext_string(const struct llext_loader *ldr, const struct llext *ext,
+	enum llext_mem mem_idx, unsigned int idx)
+{
+	return (const char *)ext->mem[mem_idx] + idx;
+}
+
+static inline uintptr_t llext_get_reloc_instruction_location(struct llext_loader *ldr,
+							     struct llext *ext,
+							     int shndx,
+							     const elf_rela_t *rela)
+{
+	return (uintptr_t) llext_loaded_sect_ptr(ldr, ext, shndx) + rela->r_offset;
+}
+
+static inline const char *llext_symbol_name(struct llext_loader *ldr, struct llext *ext,
+					    const elf_sym_t *sym)
+{
+	return llext_string(ldr, ext, LLEXT_MEM_STRTAB, sym->st_name);
+}
+/*
+ * Determine address of a symbol.
+ */
+int llext_lookup_symbol(struct llext_loader *ldr, struct llext *ext, uintptr_t *link_addr,
+			const elf_rela_t *rel, const elf_sym_t *sym, const char *name,
+			const elf_shdr_t *shdr);
+
+/*
+ * Read the symbol entry corresponding to a relocation from the binary.
+ */
+int llext_read_symbol(struct llext_loader *ldr, struct llext *ext, const elf_rela_t *rel,
+		      elf_sym_t *sym);
+
 /** @endcond */
 
 #ifdef __cplusplus

subsys/llext/llext_link.c

@@ -26,8 +26,8 @@ LOG_MODULE_DECLARE(llext, CONFIG_LLEXT_LOG_LEVEL);
 #define SYM_NAME_OR_SLID(name, slid) name
 #endif
 
-__weak int arch_elf_relocate(elf_rela_t *rel, uintptr_t loc,
-			     uintptr_t sym_base_addr, const char *sym_name, uintptr_t load_bias)
+__weak int arch_elf_relocate(struct llext_loader *ldr, struct llext *ext, elf_rela_t *rel,
+			     const elf_shdr_t *shdr)
 {
 	return -ENOTSUP;
 }
@@ -142,22 +142,31 @@ static const void *llext_find_extension_sym(const char *sym_name, struct llext *
 	return se.addr;
 }
 
-/**
- * @brief Determine address of a symbol.
- *
- * @param ext llext extension
- * @param ldr llext loader
- * @param link_addr (output) resolved address
- * @param rel relocation entry
- * @param sym symbol entry
- * @param name symbol name
- * @param shdr section header
- *
- * @return 0 for OK, negative for error
+/*
+ * Read the symbol entry corresponding to a relocation from the binary.
+ */
+int llext_read_symbol(struct llext_loader *ldr, struct llext *ext, const elf_rela_t *rel,
+		      elf_sym_t *sym)
+{
+	int ret;
+
+	ret = llext_seek(ldr, ldr->sects[LLEXT_MEM_SYMTAB].sh_offset
+		+ ELF_R_SYM(rel->r_info) * sizeof(elf_sym_t));
+	if (ret != 0) {
+		return ret;
+	}
+
+	ret = llext_read(ldr, sym, sizeof(elf_sym_t));
+
+	return ret;
+}
+
+/*
+ * Determine address of a symbol.
  */
-static int llext_lookup_symbol(struct llext *ext, struct llext_loader *ldr, uintptr_t *link_addr,
-			       const elf_rela_t *rel, const elf_sym_t *sym, const char *name,
-			       const elf_shdr_t *shdr)
+int llext_lookup_symbol(struct llext_loader *ldr, struct llext *ext, uintptr_t *link_addr,
+			const elf_rela_t *rel, const elf_sym_t *sym, const char *name,
+			const elf_shdr_t *shdr)
 {
 	if (ELF_R_SYM(rel->r_info) == 0) {
 		/*
@@ -219,7 +228,6 @@ static int llext_lookup_symbol(struct llext *ext, struct llext_loader *ldr, uint
 	return 0;
 }
 
-
 static void llext_link_plt(struct llext_loader *ldr, struct llext *ext, elf_shdr_t *shdr,
 			   const struct llext_load_param *ldr_parm, elf_shdr_t *tgt)
 {
@@ -359,7 +367,6 @@ int llext_link(struct llext_loader *ldr, struct llext *ext, const struct llext_l
 {
 	uintptr_t sect_base = 0;
 	elf_rela_t rel;
-	elf_sym_t sym;
 	elf_word rel_cnt = 0;
 	const char *name;
 	int i, ret;
@@ -446,7 +453,7 @@ int llext_link(struct llext_loader *ldr, struct llext *ext, const struct llext_l
 			return -ENOEXEC;
 		}
 
-		sect_base = (uintptr_t)llext_loaded_sect_ptr(ldr, ext, shdr->sh_info);
+		sect_base = (uintptr_t) llext_loaded_sect_ptr(ldr, ext, shdr->sh_info);
 
 		for (int j = 0; j < rel_cnt; j++) {
 			/* get each relocation entry */
@@ -460,47 +467,49 @@ int llext_link(struct llext_loader *ldr, struct llext *ext, const struct llext_l
 				return ret;
 			}
 
-			/* get corresponding symbol */
-			ret = llext_seek(ldr, ldr->sects[LLEXT_MEM_SYMTAB].sh_offset
-				    + ELF_R_SYM(rel.r_info) * sizeof(elf_sym_t));
-			if (ret != 0) {
-				return ret;
-			}
-
-			ret = llext_read(ldr, &sym, sizeof(elf_sym_t));
-			if (ret != 0) {
-				return ret;
-			}
+#ifdef CONFIG_LLEXT_LOG_LEVEL
+			if (CONFIG_LLEXT_LOG_LEVEL >= LOG_LEVEL_INF) {
+				uintptr_t link_addr;
+				uintptr_t op_loc =
+					llext_get_reloc_instruction_location(ldr, ext,
+									     shdr->sh_info,
+									     &rel);
+				elf_sym_t sym;
 
-			name = llext_string(ldr, ext, LLEXT_MEM_STRTAB, sym.st_name);
+				ret = llext_read_symbol(ldr, ext, &rel, &sym);
 
-			LOG_DBG("relocation %d:%d info 0x%zx (type %zd, sym %zd) offset %zd "
-				"sym_name %s sym_type %d sym_bind %d sym_ndx %d",
-				i, j, (size_t)rel.r_info, (size_t)ELF_R_TYPE(rel.r_info),
-				(size_t)ELF_R_SYM(rel.r_info), (size_t)rel.r_offset,
-				name, ELF_ST_TYPE(sym.st_info),
-				ELF_ST_BIND(sym.st_info), sym.st_shndx);
+				if (ret != 0) {
+					return ret;
+				}
 
-			uintptr_t link_addr, op_loc;
+				name = llext_symbol_name(ldr, ext, &sym);
 
-			op_loc = sect_base + rel.r_offset;
+				ret = llext_lookup_symbol(ldr, ext, &link_addr, &rel, &sym, name,
+							  shdr);
 
-			ret = llext_lookup_symbol(ext, ldr, &link_addr, &rel, &sym, name, shdr);
+				if (ret != 0) {
+					LOG_ERR("Could not find symbol %s!", name);
+					return ret;
+				}
 
-			if (ret != 0) {
-				LOG_ERR("Failed to lookup symbol in rela section %d entry %d!", i,
-					j);
-				return ret;
+				LOG_DBG("relocation %d:%d info 0x%zx (type %zd, sym %zd) offset %zd"
+					" sym_name %s sym_type %d sym_bind %d sym_ndx %d",
+					i, j, (size_t)rel.r_info, (size_t)ELF_R_TYPE(rel.r_info),
+					(size_t)ELF_R_SYM(rel.r_info), (size_t)rel.r_offset,
+					name, ELF_ST_TYPE(sym.st_info),
+					ELF_ST_BIND(sym.st_info), sym.st_shndx);
+
+				LOG_INF("writing relocation symbol %s type %zd sym %zd at addr "
+					"0x%lx addr 0x%lx",
+					name, (size_t)ELF_R_TYPE(rel.r_info),
+					(size_t)ELF_R_SYM(rel.r_info),
+					op_loc, link_addr);
 			}
+#endif /* CONFIG_LLEXT_LOG_LEVEL */
 
-			LOG_INF("writing relocation symbol %s type %zd sym %zd at addr 0x%lx "
-				"addr 0x%lx",
-				name, (size_t)ELF_R_TYPE(rel.r_info), (size_t)ELF_R_SYM(rel.r_info),
-				op_loc, link_addr);
 
 			/* relocation */
-			ret = arch_elf_relocate(&rel, op_loc, link_addr, name,
-					     (uintptr_t)ext->mem[LLEXT_MEM_TEXT]);
+			ret = arch_elf_relocate(ldr, ext, &rel, shdr);
 			if (ret != 0) {
 				return ret;
 			}

subsys/llext/llext_priv.h

@@ -49,12 +49,6 @@ static inline void llext_free(void *ptr)
 int do_llext_load(struct llext_loader *ldr, struct llext *ext,
 		  const struct llext_load_param *ldr_parm);
 
-static inline const char *llext_string(const struct llext_loader *ldr, const struct llext *ext,
-				       enum llext_mem mem_idx, unsigned int idx)
-{
-	return (char *)ext->mem[mem_idx] + idx;
-}
-
 /*
  * Relocation (llext_link.c)
  */